Preheat oven to 350 degrees. Mix flour, butter, and powdered sugar in an electric mixer until the dough starts to come together. Press into
an ungreased 8 x 8 inch pan, building up an edge. Bake 20 minutes, until light brown.

Wipe out bowl. Beat remaining ingredients for 3 minutes until light and fluffy. Pour over hot crust. Bake another 25 minutes longer, or just until no imprint remains when touched lightly in center. Allow to cool completely, then sprinkle with powdered sugar and cut into squares.